This invention is concerned with an enhanced method of sequentially hydraulic fracturing a subsurface formation. This invention is also concerned with a method of producing hydrocarbons from a hydrocarbon-bearing formation that has been fractured by using an enhanced sequential hydraulic fracturing method.
Hydraulic fracturing techniques have been widely used for stimulating wells penetrating subsurface or subterranean hydrocarbon-bearing formations by creating fractures which extend from the wells into the formation. These techniques normally involve injecting a fracturing fluid down a well and into contact with the subterranean formation to be fractured. A sufficiently high pressure is applied to the fracturing fluid to initiate a fracture in the formation and the fracturing fluid is injected down the well at a sufficiently high rate to propagate the fracture thereinto. Propping materials are normally entrained in the fracturing fluid and are deposited in the fracture to maintain the fracture open.
In U.S. Pat. No. 4,067,389 there is described a technique of hydraulically fracturing a subterranean formation wherein there is used a fracturing fluid comprised of an aqueous solution of an interaction product of a polysaccharide and a galactomannan.
In U.S. Pat. No. 3,547,198 there is described a method of forming two vertically disposed fractures communicating with a well equipped with a casing and which well penetrates a subterranean earth formation having a known preferred fracture orientation.
In U.S. Pat. No. 4,724,905 there is described a process for sequentially hydraulic fracturing a hydrocarbon-bearing formation penetrated by two closely spaced wells. In sequential hydraulic fracturing, the direction that a hydraulic fracture will propagate is controlled by altering the local in-situ stress distribution in the vicinity of a first wellbore. By this method, a hydraulic fracturing operation is conducted at the first wellbore wherein hydraulic pressure is applied to the formation sufficient to cause a hydraulic fracture to form perpendicular to the least principal in-situ stress.
While maintaining pressure in this first hydraulic fracture, a second hydraulic fracture is initiated in a second wellbore. This second hydraulic fracture, due to the alteration of the local in-situ stresses by the first hydraulic fracture, will initiate at an angle, possibly perpendicular, to the first hydraulic fracture.